蒙乃尔合金焊接工艺研究

蒙乃尔合金具有加工性能好、耐腐蚀性强、机械性能优良等优点,被广泛应用在加工制造业中,一定程度上推动加工制造业的发展.但蒙乃尔合金焊接作业中容易受一些不良因素影响,出现焊接缺陷,因此,如何采取针对性预防措施,不断提升焊接质量及水平,是焊接作业人员关注的重点.本文对蒙乃尔合金焊接工艺进行探讨,为提高蒙乃尔合金焊接质量及水平提供参考.     

阻尼合金在电子设备结构设计中的应用

我国电子设备发展进程逐渐加快,在材料选择方面,一直秉持性能和质量高精度的原则,近几年,将阻尼合金应用在电子设备中也成为了一种趋势,主要是由于阻尼合金具备优良的机械性能以及阻尼减振性能.本文对电子设备结构设计要求以及阻尼合金的类型进行了简要分析,并集中阐释了阻尼合金在电子设备结构设计中的应用路径,旨在为研究人员提供更加有价值的建议.     

TiAl合金显微组织分形特征及腐蚀性能研究

TiAl合金具有低密度、高强度、高硬度、高温抗蠕变强度、高温抗氧化性能及很强的耐腐蚀性能,是航天、航空及汽车用发动机等耐热结构的首选材料。通过计算TiAl合金的分形盒维数和缺项定量,分析了Ti-46.5Al(at.%)合金经不同热处理后显微组织的分形特性及其对腐蚀性能的影响。结果表明:分形盒维数基本反映出各状态TiAl合金显微组织分形结构的复杂程度,以1300℃条件下烧结保温2h的TiAl合金微观组织的分形结构最为简单,抗腐蚀性能最好,而以1040℃退火12h的最为复杂;经缺项分析得知,铸态TiAl合金的分形结构最复杂,由此导致其抗腐蚀性能最差。     

Sr对Mg-1.7Si合金中初生和共晶Mg_2Si相的变质作用

为了获得性能优良的耐热镁合金,研究了Sr对初生和共晶Mg_2Si相的变质作用,并利用扫描电子显微镜观察了Mg_2Si相的形貌特征与Mg-1.7Si-x Sr合金的微观组织.结果表明,当Sr的质量分数处于1.0%~1.5%范围内时,可对初生和共晶Mg_2Si相进行有效变质.Sr的吸附作用可以诱发孪晶沟槽、旋转晶界等原子扩展台阶的出现,引起原子堆砌方式和晶体生长方向的改变,因而Sr可对初生Mg_2Si相起到变质作用.Sr的添加还可将Mg+Mg_2Si共晶的长大方式由合作长大模式变为以重新形核为主兼有合作长大的混合模式,使得Mg_2Si相的生长形态产生改变,因而Sr可对共晶Mg_2Si起到变质作用.     

Fe_(40)Co_(40)Zr_(10)B_9M_1(M=Cu,Ge,Ag)合金的热稳定性及微观结构研究

采用单辊快淬法制备Fe40Co40Zr10B9Cu1、Fe40Co40Zr10B9Ge1和Fe40Co40Zr10B9Ag1非晶合金薄带,并对3种合金在不同温度下进行热处理.利用差热分析仪(DTA)和X射线衍射仪(XRD)等测试手段对样品的热稳定性及微观结构进行研究.结果表明:Fe40Co40Zr10B9Cu1、Fe40Co40Zr10B9Ge1和Fe40Co40Zr10B9Ag13种合金的激活能分别为262.4、267.6和252.3 k J/mol,说明Cu元素、Ge元素和Ag元素的添加对合金的热稳定性影响不大,Ge元素的添加最有利于提高合金的热稳定性.3种合金的晶化过程相似:非晶→非晶+α-Fe(Co)→α-Fe(Co)+Zr Co3B2+Fe(Co)3Zr.     

铬基钨镍钼高耐磨合金耐磨机理及产业化

本文研究了铬基钨镍钼高耐磨合金的耐磨机理。重点分析了铬基钨镍钼高耐磨合金的铸造工艺流程、铸造用废砂回收再生树脂砂的利用技术以及基于铬基钨镍钼高耐磨合金的耐磨产品。结果表明:铬基钨镍钼高耐磨合金的各种成分在不同工况中具有良好的耐磨性能。     

Refinement mechanism of in-situ Al4C3 particles on AZ91 magnesium alloys

The effects of SrCO3 on the microstructure of AZ91 magnesium alloy were investigated by OM, SEM, EDS, XRD and DTA analyses. The results show that AZ91 magnesium alloy with 1.0% SrCO3 addition has the best refining effect at 730 ℃ for 20 min, the average size of the α-Mg grain in AZ91 matrix alloy is reduced from about 91 μm to 58 μm, with reduction of about 36%. Based on the analysis results of EDS, binding energy, and Gibbs free energy, it is evident that the grain is refined because of the generation of A14 C3 particles which can be used as the crystal nucleus of the magnesium alloy when SrCO 3 is added. Owing to the generation of A14C3 in AZ91 magnesium alloy, the grain boundary is pined and the grain growth is inhibited. In the accession to the Al4C3, small subcooling temperature difference leads to the formation of fine grain microstructure in alloy melt. Fine grain microstructure in AZ91 alloy melt with the addition of SrCO3 can be obtained on the condition of lower undercooling temperature according to the DTA analysis results.     

Calculation of thermodynamic parameters of Mg-Al-Y alloy

By means of Miedema formation enthalpy model with Toop model, the excess free-energy, enthalpies of formation, excess entropies and activity values of all components of Mg-Al-Y ternary alloy were calculated with computer programming. The experimental results show that enthalpies of formation, excess freeenergy and excess entropies of the ternary alloy are negative in the whole content range, the minimum values at 1 123 K are all obtained at x Al=55%, x Y=45%, x Mg=0%, which are-37.969, –30.961 kJ/mol and-6.24 J/(mol·k) respectively. Activity curves show that the activity values of Al and Y in Mg-Al-Y ternary alloy rapidly decrease with the decrease of molar fraction, the values of which are very small when the molar fraction decreases to 0.4. It means that there is a strong interaction between Al and Y and stable compounds can be form in the Mg-Al-Y ternary alloy system.     

Mechanical,electrical, and thermal expansion properties of carbon nanotube-based silver and silver-palladium alloy composites

The mechanical, electrical, and thermal expansion properties of carbon nanotube（CNT）-based silver and silver–palladium（10：1, w/w） alloy nanocomposites are reported. To tailor the properties of silver, CNTs were incorporated into a silver matrix by a modified molecular level-mixing process. CNTs interact weakly with silver because of their non-reactive nature and lack of mutual solubility. Therefore, palladium was utilized as an alloying element to improve interfacial adhesion. Comparative microstructural characterizations and property evaluations of the nanocomposites were performed. The structural characterizations revealed that decorated type-CNTs were dispersed, embedded, and anchored into the silver matrix. The experimental results indicated that the modification of the silver and silver–palladium nanocomposite with CNT resulted in increases in the hardness and Young＇s modulus along with concomitant decreases in the electrical conductivity and the coefficient of thermal expansion（CTE）. The hardness and Young＇s modulus of the nanocomposites were increased by 30%？40% whereas the CTE was decreased to 50%-60% of the CTE of silver. The significantly improved CTE and the mechanical properties of the CNT-reinforced silver and silver–palladium nanocomposites are correlated with the intriguing properties of CNTs and with good interfacial adhesion between the CNTs and silver as a result of the fabrication process and the contact action of palladium as an alloying element.     

Microstructure and mechanical properties of AZ31 alloy ingot fabricated by semi-continuous casting

The AZ31 alloy ingot with diameter of 110 mm and length of 3500 mm was fabricated successfully. The compositions and microstructure morphologies of the ingot at different locations were performed, which indicated that the chemical composition distributed homogeneously through the whole alloy ingot and the average grain size increased from the surface to the center. The results of the EDS and element face-scanning illustrated that the eutectic compounds mainly consisted of fl-Mg17Al12 and a small amount of fl-Mgl7（AlZn）12. Furthermore, slight improvements of the strength and ductility were observed from the center to the surface along the axial direction of the alloy ingot, while both the strength and elongation to failure of the samples along the radial direction are higher than that along the axial direction. The fine grain strengthening was the main contributors to the strength of the as-casted AZ31 alloy.